At Pivotal Labs we consider ourselves to be expert pair programmers, but sometimes even we need help. We identified (thanks to a retrospective) that we were being very unbalanced in our pairings: some developers seemed to pair with each other often while rarely paring with others. We wanted a lightweight means of enforcing balanced pairing. That’s when someone remembered the pairing matrix.

Pair Programming Matrix

A blog post titled “Pair Programming Matrix” inspired us to try our own pairing matrix. It’s a grid with a cell intersecting each pair of developers. Here’s a photo from the original article:

We thought we would give it a try, only using a Google Spreadsheet with some fancy conditional formatting instead of a whiteboard

Upshot

Overall the pairing matrix serves it purpose: it helps us have much more balanced pairings. We’ve been using it for several months and will likely continue using it so long as it seems useful.

It strikes me that a pairing matrix would be a good way for team new to pair programming to add a bit of helpful structure. I would hesitate to add this structure if it’s unneeded: “if it ain’t broke, don’t fix it.”

Pros

Exposes “holes” and “hot spots” when developers are not pairing together or pairing too often

Easy to use, reset

Can be a simple way for teams new to pairing to get started

Cons

Time off skews the matrix

Does not work well when team structure fluctuates often

Becomes unwieldily with larger teams

Examples

Here are some screenshots of pairing matrices at different stages. Team structures changed and thus the featured developers were not always the same, but you get the idea.

Early in the process. We already have a hot spot!

Pairings are starting to even out.

Over time we were much more balanced.

Eventually we needed to reset.

Too big!! We abandoned this and made the team smaller.

Make Your Own Matrix

By popular demand, I have made a blank, read-only copy of our pairing matrix, complete with conditional formatting. Feel free to duplicate it and modify the copy. Please post your own modifications and optimizations in the comments.